You want it to run a bat file on the users machine? or do you want to run a bat file on the server?
if its the first one just do a link to the bat file, but then they'd have to download it an run it (otherwise it would be a massive security risk, and would only work for windows people)
if its the second, the only way I can think of atm is to use scripting language such PHP to do it by linking to a page with the code which calls the bat file and then running whatever the link is.
Sounds odd though, why do you want to do it?